Continuity mistake: When Kryten decides to be a mechanoid again, Lister gets up and grabs his jacket and swings it around his shoulders. The camera cuts to Kryten for a second then back to Lister, who now has his jacket on fully. The amount of time the camera was away from Lister would make this impossible for him to put the jacket on that quickly. (00:22:15)
Continuity mistake: In the scene where Lister is talking to human Kryten, just before Lister sees the photos, keep an eye on Lister's hat. It is perched on top of his head with about an inch of hair showing, yet the next shot shows the hat covering all of the hair, then it goes back to an inch of hair showing again. There is no time for Lister to have adjusted his hat between cuts. It is clear the line had to be re-shot. (00:12:35)
Continuity mistake: Kryten has three spare heads but in 'The Last Day' in series 3, he only packed away one head. (00:18:40)
Continuity mistake: Lister enters with a tray with some food on to give to Kryten. The position of the tray changes position between shots. (00:10:10)
Continuity mistake: When Lister has been made smaller, one shot shows him holding the bazooka, but the next shot shows him with his hand lowered. (00:25:30)
Answer: The cello is a large four-stringed instrument, which, when it is played, stands vertically on the floor between the player's legs (assuming they are seated). If it is to grow as large as the other instuments mentioned will, it would require a rather unseemly lack of femininity to be able to encompass it with the legs.
Rooster of Doom